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FATIGUE STRENGTH DETERMINATION OF BUTT WELDED JOINTS BY FEM
M.Szubryt,J.Brózda
金属学报(英文版) , 2004,
Abstract: The influence of welding parameters of butt joints, made by three processes (MMA, MAGand T.I.M.E), on their geometric characteristics has been evaluated, which in turn caused a change of the fatigue strength. That fore the statistic analysis and FEM were used and a method developed in the Institute of Welding, which consist in a direct connection of parameters used during welding with the fatigue strength of joints welded by various processes. It has been proven, among others.which by using more advanced welding processes (TLM.E) the fatigue strength of welded joints can be increased in comparison to joints welded by MMA and MAG.
Fatigue life estimation in welded joints under multiaxial loadings  [PDF]
Andrea Carpinteri,Andrea Spagnoli,Sabrina Vantadori
Frattura ed Integrità Strutturale , 2009,
Abstract: Welded joints are frequently locations for cracks initiation and propagation that may cause fatigue failure of engineering structures. Biaxial or triaxial stress-strain states are present in the vicinity of welded joints, due to local geometrical constraints, welding processes and/or multiaxial external loadings. Fatigue life evaluation of welded joints under multiaxial proportional (in-phase) cyclic loading can be performed by using conventional hypotheses (e.g. see the von Mises criterion or the Tresca criterion) on the basis of local approaches. On the contrary, the fatigue life predictions of welded joints under non-proportional (out-ofphase) cyclic loading are generally unsafe if these conventional hypotheses are used. A criterion initially proposed by the authors for smooth and notched structural components has been extended to the fatigue assessment of welded joints. In more detail, fatigue life of welded joints under multiaxial stress states can be evaluated by considering a nonlinear combination of the shear stress amplitude (acting on the critical plane) and the amplitude and the mean value of the normal stress (acting on the critical plane). In the present paper, fatigue lifetimes predicted through the proposed criterion are compared with experimental fatigue life data available in the literature, related to fatigue biaxial tests.
Fatigue assessment of load-carrying welded cruciform joints  [PDF]
T.I. Letova,S.V. Petinov
Magazine of Civil Engineering , 2013, DOI: 10.5862/mce.38.7
Abstract: T-form and cruciform joints in which the stress flow is transferred via weld material are widely applied in welded structures. A special type of these joints is presented by fillet-welded joints with incomplete penetration used by economical and manufacturing reasons. At a certain width of the cavity it becomes an active notch which in current design rules is regarded as an initial crack. In that way, fatigue life of the joint is characterized by the crack extensions towards the outer surface of weld bead. Fatigue assessment of these joints requires reliable data on the stress intensity factors values along the crack path. The results of systematic FEA-based calculations of stress intensity factors and respective S-N curves for the considered welded joints are presented. Main results obtained during this investigation can be used in solution of engineering tasks in reference to the fatigue assessment of welded cruciform joints with incomplete penetration.
New Developed Welding Electrode for Improving the Fatigue Strength of Welded Joints
Wenxian WANG,Lixing HUO,Yufeng ZHANG,Dongpo WANG,Hongyang JING,
Wenxian WANG
,Lixing HUO,Yufeng ZHANG,Dongpo WANG and Hongyang JINGCollege of Material Science and Engineering,Tianjin University,Tianjin,China

材料科学技术学报 , 2002,
Abstract: A new welding electrode, low transformation temperatur e electrode (LTTE), was introduced in this paper. It was described in design principle, mechanics, chemical compositions of their deposited metal and manufacturing methods.It was proved that the best transformation starting temperature from austenite to martensite of the deposited metal of LTTE was at about 191℃ and it was obtained by adding alloying elements such as Cr, Ni, Mn and Mo. The microstructure of the weld metal of the LTTE was low carbon martensite and residual austenite. The compressive residual stress was induced around the weld of the LTTE and the -145 MPa in compression could be obtained in middle of weld metal. The fatigue tests showed that the fatigue strength of the longitudinal welded joints welded with the LTTE at 2×106 cycles was improved by 59% compared with that of the same type of welded joints welded with conventional E5015 and the fatigue life was increased by 47 times at 162 MPa. It is a very valuable method to improve the fatigue performance of welded joints.
The effects of sheet spacing on the fatigue life of spot-welded joints  [cached]
Hassanifard S.,Zehsaz M.,Esmaeili F.
EPJ Web of Conferences , 2010, DOI: 10.1051/epjconf/20100642002
Abstract: While investigating the fatigue strength of spot-welded joints, the effects of sheet spacing or gap amounts between sheet joints may be considered as one of the most important parameters on the fatigue life duration of the joints. The main goal of the present work is to study the influence of sheet spacing on the fatigue life of 5083-O aluminium alloy spot welded tensile-shear joints. The amounts of sheet spacing are the average values over three measurements of photograph observation of the cut-off surfaces from the nugget centre of the spot-welded joints. The amounts of gap distances between spot weld sheet joints for three different electrode clamping force levels were 0.09mm, 0.11mm and 0.13mm, respectively. The values of notch strength reduction factors have been obtained at all levels of applied loads based on volumetric approach. The fatigue lives of spot welded joints have been obtained according to the volumetric method using the notch strength reduction factors and the available smooth S-N curve of 5083-O aluminium alloy sheets. The results based on the volumetric approach have been compared with the experimental fatigue test data and there is good agreement between numerical predictions and experimental results.
A Review of the Fatigue Strength of Load Carrying Shear Welded Joints  [PDF]
Filippo Berto, Abedin Gagani, Relly Victoria V. Petrescu, Florian Ion T. Petrescu
American Journal of Engineering and Applied Sciences , 2017, DOI: 10.3844/ajeassp.2017.1.12
Abstract: In the study it is shown an overview of the latest results of two types of joints of the load carrying welded shear. Tests of fatigue have been carried out on the two solutions specific design features proposed and with the aim of improving the resistance of the joints under cycling loading. By hiring the 3D models, was determined Strain Energy Density (SED), in a volume of control which surrounds the lowest point of interest. All of the experimental results have been presented in short. The synthesis shows that all data are within the range of the scattering of the proposed previously in the specialized literature for steel construction welded.
Practical methodology to evaluate the fatigue life of seam welded joints  [PDF]
K.C.Goes,G.F. Batalha,M.V. Pereira,A.F. Camarao
Journal of Achievements in Materials and Manufacturing Engineering , 2011,
Abstract: Purpose: of this paper is to present a practical and robust methodology developed to evaluate the fatigue life of seam welded joints under combined cyclic loading.Design/methodology/approach: Fatigue analysis was conducted in virtual environment. The finite element stress results from each loading were imported to fatigue code FE-Fatigue and combined to perform the fatigue life prediction using the S x N (stress x life) method. A tube-to-plate specimen was submitted to a combined cyclic loading (bending and torsion) with constant amplitude. The virtual durability analysis result was calibrated based on these laboratory tests and design codes such as BS7608 and Eurocode 3. The feasibility and application of the proposed numerical-experimental methodology and contributions for the technical development are discussed. Major challenges associated with this modelling and improvement proposals are finally presented.Findings: The finite element model was validated due to laboratory results. The analytical stress result presented upper value due to the approach used that considered the fillet weld supported all work. The model presented a good representation of failure and load correlation.Research limitations/implications: The measurement or modelling of the residual stresses resulting from the welding process was not included in this work. However, the thermal and metallurgical effects, such as distortions and residual stresses, were considered indirectly with regard to the corrections performed in the fatigue curves obtained from the investigated samples.Practical implications: Integrating fatigue analysis and finite elements, it is possible to analyse several welded joint configurations in the design phase, providing development time and cost reduction, increasing the project reliability.Originality/value: This methodology will permit, in further studies, the modelling of both stresses, in-service and residual stresses, acting together, which seem like an advantage to engineers and researchers who work in design and evaluation of structural components against fatigue failures.
Fatigue design of welded joints using the finite element method and the 2007 ASME Div. 2 Master curve  [PDF]
T. Marin,G. Nicoletto
Frattura ed Integrità Strutturale , 2009,
Abstract: Fatigue design of welded structures is primarily based on a nominal stress; hot spot stress methods or local approaches each having several limitations when coupled with finite element modeling. An alternative recent structural stress definition is discussed and implemented in a post-processor. It provides an effective means for the direct coupling of finite element results to the fatigue assessment of welded joints in complex structures. The applications presented in this work confirm the main features of the method: mesh-insensitivity, accurate crack location and life to failure predictions.
Numerical simulation and experimental studyon constant amplitude fatigue behaviorof welded cross plate-hollow sphere joints  [PDF]
Jiao Jinfeng, Lei Honggang, Chen Y Frank
- , 2018, DOI: 10.3969/j.issn.1003-7985.2018.01.010
Abstract: In order to reveal the constant-fatigue fracture form and mechanism of the welded cross plate-hollow sphere joints(WCPHSJs)and establish its formula, the WCPHSJs were fatigue tested. A total of 19 specimens were tested under constant amplitude fatigue loads using a specially designed test rig. The joint was analyzed statically by the finite element analysis(FEA), and metallographic analysis of fatigue fracture was done by the electron scanning microscope. Numerical simulation and experimental results show that the hot-spot of WCPHSJ lies at the weld toe location where severe stress is concentrated. Fatigue cracks initiate at the weld toe and then propagate circumferentially around the sphere with a diameter equivalent to the width of the cross plate up to the fatigue fracture. The initial welding defects and constructional detail constitute the main factor of fatigue failure. The S-N curves for the joints were developed through a linear regression analysis of fatigue data. A formula for calculating constant amplitude fatigue, based on the concept of the hot spot stress amplitude, is proposed.
FATIGUE CRACK GSOWTH AND CRACK CLOSURE OF SIMULATED OVER-MATCHED WELDED JOINTS
X Y Li,X T Tian,H C ZhuWeldng Division,Beijing Polytechnic University,Beijing,China National ho of Advanced Welding Technology,HIT,Harbin,China,
X. Y. Li
,X. T. Tian and H. C. Zhu

金属学报(英文版) , 2000,
Abstract: Mismatching is one of the basic characteristics of welded joints.Overmatched welded joint with a crack in hard weld is simplified as a cracked body of CCP type SHS (a hard bar sandwiched between two soft material with a crier perallel to the interface ) in this paper.Effects of mechanical heterogeneity on fatigue crack growth and crack closure of this model are studied by experimental and elastic - plastic finite element methods. It is found that, residual plastic deformation remaining in the wake of a growing crack tip, which cases crack closure,is affected the plastic deformation in adjacent soft mate- rial near by the crack tip. Both the shape of crack tip plastic zone and stress distribution ahead of crack tip in heterogeneous cracked body are different from that of homogeneous one. Crack closure (open- ing) loads are estimated by investigating the changes of crack tip opening displacement during fatigue loading, and a new model of crack oening process is presented. Because of the difference in the effect of mechanical heterogeneity on displacement of non - fatigue crack and fatigue crack, conventional CTOD can not reflect the real deformation at crack tip of SHS specimens.
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